Cardiac Dose in Locally Advanced Lung Cancer: Results From a Statewide Consortium

Can We Offset Local Recurrence in Locally Advanced Non-Small Cell Lung Cancer? The Merry-Go-Round of Radiation Dose Escalation and Stubborn Outcomes

The Oncology Grand Rounds series is designed to place original reports published in the Journal into clinical context. A case presentation is followed by a description of diagnostic and management challenges, a review of the relevant literature, and a summary of the authors' suggested management approaches. The goal of this series is to help readers better understand how to apply the results of key studies, including those published in Journal of Clinical Oncology, to patients seen in their own clinical practice.

Building Better Patient Care in Mississippi Radiation Oncology: Why Mississippi Needs a Collaborative Quality Initiative

OBJECTIVES

Cancer is an insidious and devastating disease that affects many people. Progress in mortality rate has not been realized universally across the United States, and challenges remain in how to best make up the ground that has been lost in these areas, one of which is Mississippi. Radiation therapy is a significant contributor to cancer control rates and certain challenges exist specifically regarding this treatment modality.

METHODS

The challenges of radiation oncology in Mississippi have been reviewed and discussed, with the proposal of a potential collaboration between clinical practitioners and payors to provide optimal and cost-effective radiation therapy to patients in Mississippi.

RESULTS

A similar model to that proposed has been reviewed and evaluated. This model is discussed based on its potential validity and usefulness in Mississippi.

CONCLUSIONS

Significant barriers exist in the state of Mississippi to patients receiving a consistent standard of care, regardless of their location and socioeconomic status. A collaborative quality initiative has been shown to be a boon to this endeavor elsewhere and stands to have a similar impact in Mississippi.

Knowledge-Based Quality Assurance and Model Maintenance in Lung Cancer Radiation Therapy in a Statewide Quality Consortium of Academic and Community Practice Centers

PURPOSE

Locally advanced lung cancer (LALC) treatment planning is often complex due to challenging tradeoffs related to large targets near organs at risk, making the judgment of plan quality difficult. The purpose of this work was to update and maintain a multi-institutional knowledge-based planning (KBP) model developed by a statewide consortium of academic and community practices for use as a plan quality assurance (QA) tool.

METHODS AND MATERIALS

Sixty LALC volumetric-modulated arc therapy plans from 2021 were collected from 24 institutions. Plan quality was scored, with high-quality clinical (HQC) plans selected to update a KBP model originally developed in 2017. The model was validated via automated KBP planning, with 20 cases excluded from the model. Differences in dose-volume histogram metrics in the clinical plans, 2017 KBP model plans, and 2022 KBP model plans were compared. Twenty recent clinical cases not meeting consortium quality metrics were replanned with the 2022 model to investigate potential plan quality improvements.

RESULTS

Forty-seven plans were included in the final KBP model. Compared with the clinical plans, the 2022 model validation plans improved 60%, 65%, and 65% of the lung V20Gy, mean heart dose, and spinal canal D0.03cc metrics, respectively. The 2022 model showed improvements from the 2017 model in hot spot management at the cost of greater lung doses. Of the 20 recent cases not meeting quality metrics, 40% of the KBP model-replanned cases resulted in acceptable plans, suggesting potential clinical plan improvements.

CONCLUSIONS

A multi-institutional KBP model was updated using plans from a statewide consortium. Multidisciplinary plan review resulted in HQC model training plans and model validation resulted in acceptable quality plans. The model proved to be effective at identifying potential plan quality improvements. Work is ongoing to develop web-based training plan review tools and vendor-agnostic platforms to provide the model as a QA tool statewide.

Major adverse cardiac event risk prediction model incorporating baseline cardiac disease, hypertension, and logarithmic left anterior descending coronary artery radiation dose in lung cancer (CHyLL)

BACKGROUND AND PURPOSE

In patients with locally advanced non-small cell lung cancer (LA-NSCLC) post-radiotherapy, mean heart dose (MHD) and the percent of left anterior descending (LAD) coronary artery receiving ≥15Gy (LADV15) are associated with major adverse cardiac events (MACE). We developed a MACE prediction model in this population.

MATERIALS AND METHODS

Total 701 patients with LA-NSCLC treated with curative-intent radiotherapy reviewed, split by diagnosis date into "development" (n=500) and later (n=201) "test" cohorts. Development patients were analyzed using a multivariable Cox-proportional hazard model with backward elimination scheme (Bonferroni-adjusted α=0.025). Potential predictors were selected a priori: age, coronary heart disease (CHD), Framingham Risk, hypertension, MHD, LADV15, intensity modulated radiotherapy use, and CHD and LADV15 interaction (CHD:LADV15). Cardiac doses as quadratic, square root, and logarithmic (ln[X+1]) forms were explored. Models were internally validated with bootstrapping.

RESULTS

Final model incorporated CHD, Hypertension, Logarithmic LADV15, and CHD:ln[LADV15+1] (CHyLL; β coefficients: 5.51, 1.28, 1.48, -1.36; all p<0.006; bootstrapping c-index: 0.80; test cohort c-index: 0.76). Possible risk score range: 0-8.11. MACE incidence was 6.8% and 23.6% at 48 months (p=0.041), and survival rates were 51.6% and 35.0% (p=0.099), in the low-risk (score <5.00) and high-risk (score ≥5) test groups, respectively. Using the model, calculated LADV15 constraints for patients without CHD were 11.3% and 28.3% for those with and without hypertension, respectively, to remain low-risk.

CONCLUSIONS

Pre-existing CHD, hypertension, and LADV15 were important factors in predicting MACE after radiotherapy. CHyLL has the potential to estimate personalized LADV15 constraints based on cardiac risk factors and acceptable MACE thresholds.

The Michigan Radiation Oncology Quality Consortium: A Novel Initiative to Improve the Quality of Radiation Oncology Care

PURPOSE

Numerous quality measures have been proposed in radiation oncology, and initiatives to improve access to high-complexity care, quality, and equity are needed. We describe the design and evaluate impact of a voluntary statewide collaboration for quality improvement in radiation oncology initiated a decade ago.

METHODS AND MATERIALS

We evaluate compliance before and since implementation of annual metrics for quality improvement, using an observational dataset with information from over 20,000 patients treated in the 28 participating radiation oncology practices. At thrice-yearly meetings, experts have spoken regarding trends within the field and inspired discussions regarding potential targets for quality improvement. Blinded data on practices at various sites have been provided. Following Standards for Quality Improvement Reporting Excellence (SQUIRE) guidelines, we describe the approach and measures the program has implemented. To evaluate impact, we compare compliance at baseline and now with active measures using mixed effects regression models with site-level random effects.

RESULTS

Compliance has increased, including use of guideline-concordant hypofractionated radiotherapy, doses to targets/normal tissues, motion management, and consistency in delineating and naming contoured structures (a precondition for quality evaluation). For example, use of guideline-concordant hypofractionation for breast cancer increased from 47% to 97%, adherence to target coverage goals and heart dose limits for dose increased from 46% to 86%, motion assessment in patients with lung cancer increased from 52% to 94%, and use of standard nomenclature increased from 53% to 82% for lung patients and from 80% to 94% for breast patients (all p<0.001).

CONCLUSIONS

Although observational analysis cannot fully exclude secular trends, contextual data revealing slow uptake of best practices elsewhere in the US and qualitative feedback from participants suggests that this initiative has improved the consistency, efficiency, and quality of radiation oncology care in its member practices and may be a model for oncology quality improvement more generally.

Effect of education and standardization of cardiac dose constraints on heart dose in lung cancer patients receiving definitive radiation therapy across a statewide consortium

PURPOSE/OBJECTIVES

Cardiac radiation exposure is associated with an increased rate of adverse cardiac events in patients receiving radiation therapy for locally advanced non-small cell lung carcinoma (NSCLC). Previous analysis of practice patterns within XXXX revealed 1 in 4 patients received a mean heart dose >20 Gy and significant heterogeneity existed among treatment centers in using cardiac dose constraints. The purpose of this study is to analyze the effect of education and initiation of standardized cardiac dose constraints on heart dose across a statewide consortium.

MATERIALS/METHODS

From 2012 to 2020, 1681 patients from 27 academic and community centers who received radiation therapy for locally advanced NSCLC were included in this analysis. Dosimetric endpoints including mean heart dose (MHD), mean lung dose, and mean esophagus dose were calculated using data from dose-volume histograms. These dose metrics were grouped by year of treatment initiation for all patients. Education regarding data for cardiac dose constraints first occurred in small lung cancer working group meetings and then consortium-wide starting in 2016. In 2018, a quality metric requiring mean heart dose <20 Gy while maintaining dose coverage (D95) to the target was implemented. Dose metrics were compared before (2012-2016) versus after (2017-2020) initiation of interventions targeting cardiac constraints. Statistical analysis was performed using the Wilcoxon Rank Sum test.

RESULTS

Following education and implementation of the heart dose performance metric, mean MHD declined from an average of 12.2 Gy pre-intervention to 10.4 Gy post-intervention (p < 0.0001), and the percentage of patients receiving MHD >20 Gy reduced from 21.1% to 10.3% (p < 0.0001). Mean lung dose and mean esophagus dose did not increase, and target coverage remained unchanged.

CONCLUSIONS

Education and implementation of a standardized cardiac dose quality measure across a statewide consortium was associated with a reduction of mean heart dose in patients receiving radiation therapy for locally advanced NSCLC. These dose reductions were achieved without sacrificing target coverage, increasing mean lung dose, or increasing mean esophagus dose. Analysis of the clinical ramifications of the reduction in cardiac doses is ongoing.

A Promising Treatment Strategy for Lung Cancer: A Combination of Radiotherapy and Immunotherapy

Lung cancer is a leading cause of cancer-related deaths worldwide despite advances in treatment. In the past few decades, radiotherapy has achieved outstanding technical advances and is being widely used as a definitive, prophylactic, or palliative treatment of patients with lung cancer. The anti-tumor effects of radiotherapy are considered to result in DNA damage in cancer cells. Moreover, recent evidence has demonstrated another advantage of radiotherapy: the induction of anti-tumor immune responses, which play an essential role in cancer control. In contrast, radiotherapy induces an immunosuppressive response. These conflicting reactions after radiotherapy suggest that maximizing immune response to radiotherapy by combining immunotherapy has potential to achieve more effective anti-tumor response than using each alone. Immune checkpoint molecules, such as cytotoxic T-lymphocyte-associated protein 4, programmed cell death-1/programmed death-ligand 1, and their inhibitors, have attracted significant attention for overcoming the immunosuppressive conditions in patients with cancer. Therefore, the combination of immune checkpoint inhibitors and radiotherapy is promising. Emerging preclinical and clinical studies have demonstrated the rationale for these combination strategies. In this review, we outlined evidence suggesting that combination of radiotherapy, including particle therapy using protons and carbon ions, with immunotherapy in lung cancer treatment could be a promising treatment strategy.

An Institutional Audit of Maximum Heart Dose in Patients Treated With Palliative Radiotherapy for Non-small Cell Lung Cancer

BACKGROUND/AIM

Recent studies suggested that high unintended radiation doses to the heart may reduce survival of patients with non-small-cell lung cancer (NSCLC) irradiated with curative intent. In the palliative setting, limited information is available. Therefore, we analyzed a single-institution cohort of 165 patients.

PATIENTS AND METHODS

Patients in this retrospective study received palliative (chemo)radiotherapy (at least 30 Gy). Typical radiation doses were 10-13 fractions of 3 Gy and 15 fractions of 2.8 Gy. Heart dose constraints were not employed during treatment planning. The maximum dose to 1 cc of the heart was registered and converted into the equivalent dose in 2-Gy fractions (EQD2).

RESULTS

The median heart dose (maximum to 1 cc) was 26 Gy (range=11-42 Gy). This dose corresponded to 28-108% of the prescription dose. After conversion into EQD2, the median maximum heart dose to 1 cc was 26 Gy, range=10-58 Gy). Neither higher T-stage nor higher N-stage predicted for higher maximum heart EQD2. The maximum heart EQD2 was not associated with overall survival.

CONCLUSION

The current practice of focusing on sparing of lungs and esophagus appears acceptable in the context of palliative regimes. To further strengthen this strategy, additional studies looking at cardiac substructures and other dosimetric variables such as mean dose are warranted.

Particle Beam Therapy for Cardiac-Sparing Radiotherapy in Non-Small Cell Lung Cancer

Radiation therapy plays an integral role in the treatment of all stages of non-small cell lung cancer. Survival outcomes are improving, but radiation therapy remains associated with long-term toxicity. Recently, it has become evident that the heart is an important organ at risk for treatment-related morbidity. In this review, we discuss the hypothesis that particle radiation therapy offers superior dosimetry compared with photon-based treatment, and that this comparative advantage translates into clinically meaningful cardiac toxicity reduction with similar local tumor control. We discuss the evidence in non-small cell lung cancer to date, the ongoing prospective trials that may provide additional insight, and the opportunities to optimally integrate particle therapy into future prospective investigation.

Stereotactic body radiotherapy (SBRT) for central and ultracentral node-negative lung tumors

Advancements in imaging and radiotherapy (RT) techniques have allowed for remarkably precise delivery of high radiation dose per treatment fraction to intrathoracic targets. As a non-invasive therapeutic modality (compared to surgery), stereotactic body radiotherapy (SBRT) is an attractive option for patients with early-stage non-small cell lung cancers and oligometastases, especially for older patients with significant comorbidities and pre-existing pulmonary dysfunction. However, the outcomes and side effect profile of SBRT are highly dependent on tumor location, especially if the tumor is located centrally (within 2 cm of the proximal bronchial tree (PBT)] or ultracentrally (touching or within 1 cm of the mediastinum, esophagus, and PBT). In this focused review, we will examine the contemporary practice and principles of using hypofractionated RT or SBRT for central and ultracentral thoracic tumors. We will identify future directions on how this practice may be incorporated into the increasingly complicated modern paradigm of lung cancer treatments which now include immunotherapy along with proton beam radiotherapy.

Incorporating sensitive cardiac substructure sparing into radiation therapy planning

PURPOSE

Rising evidence suggests that cardiac substructures are highly radiosensitive. However, they are not routinely considered in treatment planning as they are not readily visualized on treatment planning CTs (TPCTs). This work integrated the soft tissue contrast provided by low-field MRIs acquired on an MR-linac via image registration to further enable cardiac substructure sparing on TPCTs.

METHODS

Sixteen upper thoracic patients treated at various breathing states (7 end-exhalation, 7 end-inhalation, 2 free-breathing) on a 0.35T MR-linac were retrospectively evaluated. A hybrid MR/CT atlas and a deep learning three-dimensional (3D) U-Net propagated 13 substructures to TPCTs. Radiation oncologists revised contours using registered MRIs. Clinical treatment plans were re-optimized and evaluated for beam arrangement modifications to reduce substructure doses. Dosimetric assessment included mean and maximum (0.03cc) dose, left ventricular volume receiving 5Gy (LV-V5), and other clinical endpoints. As metrics of plan complexity, total MU and treatment time were evaluated between approaches.

RESULTS

Cardiac sparing plans reduced the mean heart dose (mean reduction 0.7 ± 0.6, range 0.1 to 2.5 Gy). Re-optimized plans reduced left anterior descending artery (LADA) mean and LADA_0.03cc (0.0-63.9% and 0.0 to 17.3 Gy, respectively). LV_0.03cc was reduced by >1.5 Gy for 10 patients while 6 cases had large reductions (>7%) in LV-V5. Left atrial mean dose was equivalent/reduced in all sparing plans (mean reduction 0.9 ± 1.2 Gy). The left main coronary artery was better spared in all cases for mean dose and D_0.03cc . One patient exhibited >10 Gy reduction in D_0.03cc to four substructures. There was no statistical difference in treatment time and MU, or clinical endpoints to the planning target volume, lung, esophagus, or spinal cord after re-optimization. Four patients benefited from new beam arrangements, leading to further dose reductions.

CONCLUSIONS

By introducing 0.35T MRIs acquired on an MR-linac to verify cardiac substructure segmentations for CT-based treatment planning, an opportunity was presented for more effective sparing with limited increase in plan complexity. Validation in a larger cohort with appropriate margins offers potential to reduce radiation-related cardiotoxicities.

Current radiotherapy techniques in NSCLC: challenges and potential solutions

Introduction: Radiotherapy is an important therapeutic strategy in the management of non-small cell lung cancer (NSCLC). In recent decades, technological implementations and the introduction of image guided radiotherapy (IGRT) have significantly increased the accuracy and tolerability of radiation therapy.Area covered: In this review, we provide an overview of technological opportunities and future prospects in NSCLC management.Expert opinion: Stereotactic body radiotherapy (SBRT) is now considered the standard approach in patients ineligible for surgery, while in operable cases, it is still under debate. Additionally, in combination with systemic treatment, SBRT is an innovative option for managing oligometastatic patients and features encouraging initial results in clinical outcomes. To date, in inoperable locally advanced NSCLC, the radical dose prescription has not changed (60 Gy in 30 fractions), despite the median overall survival progressively increasing. These results arise from technological improvements in precisely hitting target treatment volumes and organ at risk sparing, which are associated with better treatment qualities. Finally, for the management of NSCLC, proton and carbon ion therapies and the recent development of MR-Linac are new, intriguing technological approaches under investigation.